import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:递归求和
 * User: xwl
 * Date: 2023-04-03
 * Time: 19:31
 */
public class Test3 {
    public static void main(String[] args) {
        //输入
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        //调用函数
        int ret = add(n);
        //输出
        System.out.println(ret);
    }
    //递归求和
    public static int add(int n) {
        if(n == 1) {
            return 1;
        }else if(n > 1) {
            return n + add(n-1);
        }else {
            return 0;
        }
    }

}
